Gnu Octave is a completely different program than Notepad++, and has nothing to do with the Notepad++ project. It may have its own plugins directory, but that has nothing to do with Notepad++. If Octave bundles a Notepad++ copy with their distribution (which they are legally allowed to do, based on the LICENSE), then maybe there really is a Notepad++\Plugins directory there. But that would mildly surprise me (and some quick poking at Octave’s site doesn’t show me any obvious reference from Octave to Notepad++).
Those .tmp files and rar folders likely have nothing to do with Notepad++.
I think you’ve done a lot of mucking around, and you are in a strange situation. We are not generic tech support / Windows support, and if you are having problems at bootup, and if you don’t have Notepad++ left on your machine, then the problem is a Windows problem, not a Notepad++ problem. I don’t know how you got to where you are, but I don’t think we can help you out of the mess you’re in now.
Sorry to not have better news for you. Good luck.